1. Field of the Invention
This invention relates to a sound effect-creating device used in electronic musical instruments and the like, and more particularly to a sound effect-creating device which is adapted to determine a predetermined modulation frequency (frequency of a modulating wave) based on a repetition period of a timing clock of a MIDI signal, or vice versa, in imparting a modulation effect to a musical tone.
2. Prior Art
In performance of a musical instrument or the singing of a song (hereinafter simply referred to as "the performance"), it is a known technique for making the performance sound natural to impart a modulation effect, such as a vibrato effect or a tremolo effect to elongated portions of the sustain sound. To make use of this technique, a sound effect-creating device comprising a modulator is generally used today, i.e., at the age of rapid progress in the art related to electronic musical instruments, thereby imparting the modulation effect to the performance.
In imparting the modulation effect to the performance by the use of such a sound effect-creating device, it is a conventional method that an operator of the sound effect-creating device determines a modulation frequency based on the operator's sense, or otherwise the operator calculates the modulation frequency based on the tempo of the performance, whenever it is required, or determines the modulation frequency by the use of a converting table set beforehand therefor, and then the operator sets the thus obtained modulation frequency to the modulator of the sound effect-creating device.
However, this method has the following inconveniences: First, it is naturally required to make the tempo of performance of an electronic musical instrument playing an accompaniment completely synchronous with the modulation frequency for modulating the musical tone signal of the performance. Otherwise, the vibration of the musical tone caused by the modulation does not agree with the accompaniment, and impedes the performance to the contrary. According to the conventional method, the modulation frequency of the sound effect-creating device for modulating the musical tone signal is set by the operator separately from or independently of the electronic musical instrument for the accompaniment, which prevents the tempo of the accompaniment of the electronic musical instrument from being completely synchronous with the modulation frequency for modulating the musical tone signal and hence with the resulting vibration (vibrato or tremolo) of the musical tone. Furthermore, if the tempo of the performance or the accompaniment is changed during the performance, it is impossible to change setting of the modulation frequency, since this will impede progress of the performance.
Secondly, such calculation or use of the converting table in determining the modulation frequency is not preferred, since it is not only troublesome but also unbecoming to the performance of music which should be based on sensitivity by nature.